Party line selective signaling system having code and conference call



Nov. 3, 1953 c. E. LOMAX 2,658,110

PARTY LINE SELECTIVE SIGNALING SYSTEM HAVING CODE AND CONFERENCE CALL Original Filed Dec. 50, 1947 12 Sheets-Sheet 1 FIG.

IN VEN TOR. CLARENCE E. LOMAX AT TORN EY LINE EQUIPMENT Nov. 3, 1953 MAX 2,658,110

C. E. LO PARTY LINE SELECTIVE SIGNALING SYSTEM HAVING CODE AND CONFERENCE CALL Original Filed Dec. 50, 1947 l2 Sheets-Sheet 2 cwo FIG. 2 @70 1 c|eo I H9 1( 2 I 3 1 l 2 FIG. I3 6 7 a] 3 4 FIG. l4 ZA 3 I TO OTHER 4'90 STATIONS I907 KEY CONFERENCE INVENTOR.

CLARENCE E. LOMAX AT QB Y NOV. 3, 1953 c E LOMAX 2,658,110

PARTY LINE SELECTIVE SIGNALING SYSTEM HAVING CODE AND CONFERENCE CALL Original Filed Dec. 30, 1947 12 Sheets-Sheet 3 Cl IO 2A c170 also A cleo C Q; FR T R T= I09 zzcgilw glzzj 231 s e 022* Egg E .11

TO OTHER STATIONS J I OTHER STATIONS TWO GROUP CONFERENCE INVENTOR.

CLARENCE E. LOMAX ATTORNEY Nov. 3, 1953 C. E. LOMAX PARTY LINE SELECEIVE SIGNALING SYS HAVING CODE AND CONFERENCE CALL Original Filed Dec. 30, 1947 TEM 12 Sheets-Sheet 4 cwo 27 CI8OJ 272;,

H J T 0290 27o OOTHER H STATIONS |9o7 MULTI GROUP CONFERENCE INVENTOR.

CLARENCE E. LOMAX ATTORNEY C. E. LOMAX PARTY LINE SELECTIVE SIGNALING SYSTEM Nov. 3, 1953 HAVING CODE AND CONFERENCE CALL. so, 1947 12 Sheets-Sheet 5 Original Filed Dec.

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PARTY LINE SELECTIVE SIGNALING SYSTEM HAVING CODE AND CONFERENCE CALL Original Filed Dec. 50, 1947 12 Sheets-Sheet 6 TOMULTLGROUP CONFERENCE 5 PAGING F0 INVENTOR.

CLARENCE E. LOMAX ATTORNEY FIG 4 CONNECTOR C. E. LOMAX PARTY LINE SELECTIVE SIGNALING SYSTEM Nov. 3, 1953 HAVING CODE AND CONFERENCE CALL 30, 1947 12 Sheets-Sheet 7 Original Filed Dec.

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PARTY LINE SELECTIVE SIGNALING SYSTEM HAVING CODE AND CONFERENCE CALL Original Filed Dec. 30, 1947 12 Sheets-Sheet 10 h u w :v

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INVENTOR. CLARENCE E. LOMAX ATTORNEY 1953 c. E. LOMAX ,110

PARTY LINE SELECTIVE SIGNALINGSYSTEM HAVING CODE AND CONFERENCE CALL Original Filed Dec. 50, 1947 12 Sheets-Sheet 11 FIG. 9

L MULTI GROUP CONFERENCE 3951;

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CLARENCE E. LOMAX ATTORNEY Nov. 3, 1953 c; E, LOMAX PARTY LINE SELECTIVE SIGNALING SYSTEM HAVING CODE AND CONFERENCE CALL so, 1947 12 Sheets-Sheet 12 Original Filed Dec.

FIG. IO

MULTI GROUP CONFERENCE TO GROUP I TO GROUP *2 263 TO }OTHER GROUPS ATTORNEY Patented Nov. 3, 1953 PARTY LINE SELECTIVE SIGNALING SYS- TEM HAVING CODE AND CONFERENCE CALL Clarence E. Lomax, Chicago, 111., assignor to Automatic Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Original application December 30, 1947, Serial N0. 794,601. Divided and this application April 12, 1950, Serial No. 155,546

13 Claims. 1

The present invention relates in general to automatic telephone systems, but is more particularly concerned with small systems which are commonly known as private automatic exchanges, or as P. A. X's, and is a division of my prior application filed December 30, 1947, Serial No. 794,601, and issued May 15, 1951, as United States Patent No. 2,552,799. Exchanges of this nature are usually installed by private concerns, and in order to meet the more exacting requirements of the subscribers in these small systems, it is often necessary to provide various special features which are unnecessary in a large public exchange. The present invention is concerned with the above-mentioned special features which are commonly known as code calling, conference call ng, executive cut-in or right-of-way and party line service.

The principal object of the invention is to provide certain new and improved circuit arrangements, whereby, the above-named special features are provided without materially increasing the cost of the equipment, while retaining simple, efficient and modern high-class telephone service.

One of the features of the invention relates to improved circuit arrangements, whereby, the rotary switch as described in the co-pending application of Kenneth W. Graybill et al., Serial No. 654,556, filed March 15, 1946, now abandoned, is utilized in applicants illustrated finder, connector, code call and conference call equipment.

Another feature of the invention relates to an improved line equipment and circuit, whereby, during conference calls other parties on the lines that contain a conference member are totally disconnected from their respective lines during the conference call.

Another feature of the invention relates to improved circuit arrangements, whereby, party line service, code call, conference service and executive cut-in service can all be given in the :same exchange.

Still another feature relates to conference service, whereby, various types of conference service can be provided, with the requirements of the particular exchange controlling the type service to be used.

Other features, together with the ones named above, will be explained hereinafter, reference being had to the accompanying. drawings which show by means of the usual circuit diagrams a sufficient amount of apparatus to enable the invention to be described and understood,

Referring now to the drawings, Figures 1 to 15, inclusive:

Figure 1 shows four lines having two substa tions each, such as A and A on one line and D and D on another, etc. Substations A, B and C' are shown as conference members, hence, the cut-through relays such as I00, III! and I2!) are provided. Substation A is shown as belonging to an executive and is provided with the executive cut-in non-locking push button I18. Substation A is also provided with the non-locking push button I58 which enables the originating of the key-type conference call (push button IE8 is used only when Figure 2 is a part of the exchange). The line containing substations D and D is provided with no special features and therefore, only local or regular calls can be handled. Combined line and cut-off relays such as I30, I40, I50 and I60 are individual to each line.

Figures 2, 2A and 2B are used only when the exchange is to include conference calling, with each of the Figures 2, 2A and 23 being individual to a certain type of conference service. It is to be remembered that only one type conference can be used at a time, therefore, only one of the Figures 2, 2A or 2B can be used at a time. It

will be noted that each of the figures have been drawn so as to be easily substituted for the other and to readily connect between Figure 1 and the adjoining figures. It will also be noted that the ring cut-01f and battery feed relays individual to each line that is provided with conference service, are given the same number and location in each of figures and that the functions of the above mentioned relays are identical in each figure. However, the relays in the respective right-half portions of each figure are different. In Figure 2 a single conference group is provided, substations A, B, and C being the conference members, with one of the substations such as A having a key for initiating the conference call. In Figure 2A two-conference group service is shown with substations A and C being individual to groups I and 2 respectively and substation B being common to both groups. In Figure 2B multi-group conference service is shown, with only two groups illustrated. Substations A and C are again in different groups and substation B is common to both.

Figures 3 and 4 show one of the finder-connector links of the exchange.

Figure 5 shows the distributor.

Figures 6, 7 and 8 show the code call equipment, with Figure 6 showing the code call finder,

' tacts [6 through 25.

Figure 7 showing the pulsing circuit and code selecting equipment and Figure 8 showing the code sounding equipment.

Figures 9 and 10 show the multi-group conference equipment, with Figure 9 showing the group conference finder and Figure 10 shows the group selecting equipment.

Figures 11, 12, 13, 14 and 15 are figure-number diagrams and show the drawing arrangements for the descriptions of the sections entitled Regular P. A. X service, Key conference, Code call, Two group conference and Multi-group conference, respectively.

Having briefly described the apparatus involved in each figure, a more detailed description of the various operations will follow:

It is to be remembered that the maximum number of lines served by an exchange of this type is lines, and the number of finder connector links may be limited to not more than four. Four lines have been shown, with two parties each and so arranged as to be rung on the opposite sides of the lines. The equipment at each substation consists of the well-known, dial,

receiver, transmitter and ringer, therefore only the ringer connections at each substation have been shown, likewise the illustrated substations call numbers. All regular call numbers are two- I digit numbers and assuming that a full capacity of 20 lines are in use and also assuming each line has two parties the call numbers will be arranged in the following order: the digits 31 to and 41 to will be used for the first ten lines and I the digits 51 to and 61 to 60 will be used for The digits 31 to 30 and 51' the second ten lines. to 50 will cause the ringing to be applied to the positive line conductors and the digits 41 to 40 and 61 to 60 will cause ringing to be applied to the negative line conductors.

A rotary switch having 26 positions with 25 bank contacts has been utilized wherever applicable in the exchange. The 26th position is the normal home position for the wipers, while the first and second contacts of the connector rotary switch may be used for either code call or two-group conference service, the third and fourth contacts of the same switch utilized for the first digit of the call number when dialing the first group of ten lines and the 15th contact is used as a stopping point for the first digit of the call number when dialing the second group of ten lines. Thus, it will be seen that the first group of ten lines uses contacts 5 through 14 and the second, or last, group of ten lines uses con- The rotary switch of the finders (including the code call finder and con ference call finder and group selector) are of the non-numerical type and therefore do not use the 26th or "home position, whereas, the rotary switch of the connector and code ringing selector are numerical and do use their home positions.

Referring to Figure 1 for the present, the combined line and cut-off relays such as I30, I40, I50 and it!) are actually a two-step relay having two separate and distinct operations, the first operation closing only the x marked contacts and the second operation actuating the remaining contacts. The first operation compares with that of a line relay and the second operation comparing with the action of a cut-off relay.

Referring now to Figure 5, the distributor as shown, is of the rotary type, pre-selecting the next free or idle finder-connector link after each normal operation. Therefore during normal opcrating periods of the exchange. the p s of the rotary switch will be resting on an idle link. A busy link will apply a ground potential to the wipers and hence complete a circuit to the rotary switch motor magnet to cause the magnet to step its wipers off the grounded contact. Therefore, it will be seen that the motor magnet causes the switch to hunt for an absence of ground on its wipers.

It will be remembered that in the illustrated exchange, energization of all the rotary switch motor magnets only prepares the switch for stepping and that the actual stepping of the switch takes place upon the deenergization and release of the magnet.

The illustrated finder-connector link (Figures 3 and 4) has been drawn showing alternative connections to the finder and connector for an exchange including Two-Group Conference Service, or Multi-Group Conference Service, or Code Call Service, the type of special service used being dependent on the requirements of each individual exchange.

Referring to Figures 6, 7 and 8 the finder (Figure 6) of the code call equipment functions nearly the same as the line finder in Figure 3 with the exception that it searches for a ground potential by way of its extra control (EC) conductor instead of the control (C) conductor. The rotary switches shown in Figure '7 operate under pulsing during dialing of the code call number. As only the first five contacts of the above-named switches are used, and the code call number contains two digits; the number of codes that can be sent is limited to 25. Therefore, the maximum digital value that either digit can attain is 5. From the foregoing it will be understood that the lowest code call number will be 11 and the highest will be 55. The rotary switches in Figure 8 are of the previously mentioned 25 point type. The push button such as 865 may be conveniently located throughout the building or buildings within which the exchange is installed and may be operated for sounding special alarms such as fire, dismissal signals, etc. The alarms or gongs such as 810 and 880 (as many may be used as necessary) are also conveniently located so as to be clearly audible to everyone.

Referring to Figures 9 and 10 showing the mul- 'ti-group conference equipment, the conference finder (Figure 9) functions the same as the code call finder. The 26 point rotary switch shown in Figure 10 responds to the group number dialed.

As the switch is shown, it is wired for five conferen-ce groups, however, it may be wired to include ten conference groups, if desired. From the foregoing, it will be understood that the conference group call number is a single digit and may extend from 1 through 0, though the drawing shows it to be limited from 1 through 5.

The figure-number Diagrams 11 through 15 show the arrangement of the drawings for regular, or local, calls and for each special service. It will be remembered that regular calls may be made with each special service or combination of special services.

A detailed operational description of regular calls and all special services will follow, references being had with the drawings which show sufficient apparatus as deemed necessary for each explanation.

Regular P. A. X service The operation of the equipment (excluding all special services) as to the initiation and completion of a regular P. A. X call will now be discussed.

Referring in particular to the figure-number diagram of Figure 11 and its associated drawings comprising Figures 1, 3, 4 and 5, sufiicient apparatus of the system is shown as deemed necessary for the explanation.

Assuming that subscriber B is given a designated call number such as 32 and that subscriber D desires to call subscriber B, the equipment will operate in the following manner:

When subscriber D removes the receiver, a loop is closed across his talking conductors and a circuit is completed to the line and cut-off relay I66, this circuit extending from ground at contacts I63, the associated positive talking conductor, the loop circuit, the associated negative talking conductor, contacts I61, upper winding of relay I60 and the lower winding of relay 69 to battery. As previously described, the relay I60 is a two-step line and cut-ofi relay having two serially connected windings, capable (during the present energization) of causing the relay I 65 to close only the as contacts. At 2: contacts I62, relay I60 applies battery potential to the control conductor I56. At contacts I65, relay I69 applies a ground potential to the distributor-start conductor I90, completing a circuit to the distributor-start relay H3 (providing that the wipers of the distributor motor magnet 515 are resting on an idle finderconnector link), this circuit extending from ground at contacts 64, "12 contacts I65, conductor I90, contacts 502, high resistance winding of distributor-start relay 5I0, contacts 50I,

516 and through the marginal winding of motor magnet 515 to battery. Magnet 515 will not operate in series with relay 5 I 0.

As previously mentioned, the distributor is of the rotary type and after each normal operation preselects the next idle or free finder-connector link, therefore wipers 555 and 506 of the associated motor magnet 515 will rest on an idle or free link. However, if all links were busy at the moment, the operating circuit of the alllinks-busy relay 500 would be open due to the absence of ground potential (supplied by any, idle or free link from ground at contacts such as 354 in Figure 3) on the conductor 551 to relay 500. Relay 590 would then restore and open the circuit to motor magnet 515 at contacts 59L thereby preventing motor magnet 515 from operating. However, as soon as a link becomes free, the ground potential is restored to the conduotor 551 and relay 559 will operate and prepare a circuit to motor magnet 515. This circuit will be completed if wiper 565 is resting on a contact terminating the guard lead of a busy link, but if the wiper is resting on a contact terminating the guard lead of an idle link, the circuit will not be completed. As shown in Figure 5, the wipers 565 and 506 of magnet 515 are resting on the contacts of the illustrated finder-connector link (Figures 3 and 4) which is shown as idle.

In operating contacts 5i I, distributor-start relay 5H3 opens a mint in the energizing circuit of motor magnet 515, at contacts 5I2 ground is removed from a secondary kick-oi? circuit which is under control of the calling subscriber and relay 536, at contacts 553 a circuit is completed for relay 529 which at the moment is slightly slow to operate due to its short circuited upper winding. At contacts 5114 relay 5I9 applies a ground to the multiple circuit for maintaining relay 500' operated, at contacts 515 prepares an operating circuit for the relay 550 and at contacts 5"; completes an obvious preenergizing circuit for relay 550. Resistance R2 is high enough to prevent relay 550 from operating, but making relay 550 quick-acting to any splash of current through its upper winding and operative for any such splash.

In operating, relay 520 completes a circuit for the slow-to-operate relay 530, from ground at contacts 52I and at contacts 522 prepares a circuit for relay 560.

In operating relay 530 completes a circuit to the finder-start relay 329 (Figure 3) at contacts 53!, this circuit extending from ground at contacts 53I, wiper '506 and its associated contact, conductor 541 and the winding of relay 329 to battery. At contacts 532 relay 530 prepares a circuit for motor magnet 515, at contact 533 a kick-off circuit is prepared for motor magnet 515, at contacts 53% the circuit of the upper winding of relay 520 is opened, thereby giving relay 520 a normal quick restoring time interval. At contacts 535 relay 530 connects a ground to the multiple circuit of relay 505 and applies ground at contacts 536, thereby preparing cir cuits for motor magnet 390 and finder cutthrough relay 300.

In operating contacts 32L relay 329 completes an obvious circuit for line relay 330 at contacts 322 a circuit is prepared for the finder cutthrough relay 360, at contacts 323 a circuit is prepared for the preenergized relay 550 and at contacts 324 completes a circuit for the finder motor magnet 390, this circuit extending from round at contacts 536, contacts 54!, 552, conductor 5|, contacts 325, 391 and through the winding of magnet 390 to battery.

In operating contacts 33I, line relay 330 completes an obvious circuit for the slow-to-release hold relay 340. In operating contacts 34, hold relay 340 prepares a circuit for operating the line and cut-ofi relay I completely, at contacts 342 a pulsing circuit is prepared to the connector motor magnet 490 and at contacts 343 a point in the release circuit of the motor magnet 490 is opened.

During the operation in the preceding paragraph, magnet 390 in operating completes an obvious circuit to the interrupter relay 549 at contacts 39I. Relay 549, in operating contacts 54!,

opens the previously traced operating circuit of magnet 390, allowing magnet 390 to restore. In restoring, magnet 399 advances rotary wipers 326, 321, 328 and 329 one step, and opens the circuit to relay 540 by way of contacts 39!. In restoring, relay 540 again completes the previously traced circuit to magnet 390 by way of contacts 54L Magnet 390 reenergizes and at contacts 39I again completes the circuit to relay 540. Relay 540 energizes and at contacts 5M opens the circuit to magnet 399 allowing it to restore. In restoring, magnet 396 advances wipers 326, 321, 328

and 329 a second step and at contacts 3! again opens the circuit to relay 540 allowing it to restore. This interaction between magnet 390 and relay 540 continues until wiper 326 engages the contact terminating control conductor I56, at which time a circuit is completed for the preenergized relay 550, this circuit extending by way of ground at contacts SI 5, upper winding of relay 550, conductor 521, contacts 323, wiper 323 and its engaged contact, conductor I 56, cable C-I10, conductor I56, as contact I62 and the lower winding of relay I60 to battery.

in operating contacts 552, relay 550 opens the circuit to magnet 380 and at contacts 55I completes a circuit to the finder cut-through relay 300, this circuit extending from ground at contacts 536, contact 54I, 55I conductor 531, contacts 332 and the winding of relay 300 to battery. At contacts 553 an obviou circuit is completed to the total call meter 585 for registering each call and at contacts 554 a locking circuit of relay 510 is opened. It is to be remembered that wipers 326, 321, and 329 are also resting on contacts in their respective banks corresponding to the contact upon which wiper 328 is resting.

In operating contacts 30I and 303, finder cutthrough relay 300 completes the extension of the talking conductors from the calling line with the finder-connector link, at contacts 302 a circuit is completed for the transmission of dial tone out over the positive talking conductor to the calling station as an indication of readiness by the link to receive dialing. At contacts 304, relay 300 completes the circuit for the complete operation of relay I60, this circuit extending from ground at contacts 34I, contacts 304 wiper 328 and its associated contact, conductor I56, cable C-I10, conductor I56, as contacts I62 and the lower winding of relay I60 to battery. The closing of contacts 304 also shunts the upper winding of relay 550, but since relay 550 has operated, it will remain so by the holding effect of its lower winding. The ground potential at contacts 34I busies subscriber D to other finders and is also applied to the rotary connector switch by way of conductor I66 to busy subscriber D to incoming calls. At contacts 305, relay 300 completes an obvious holding circuit for itself by way of ground at contacts 34I. At contacts 306, relay 300 prepares a future locking circuit for relays 380 and 400, and supplies a working ground for various other relays in the finder-connector link, at contacts 301 the interrupting circuit to motor magnet 390 is opened, at contacts 308 a circuit is completed for energizing motor magnet 515, this circuit extending from ground at contacts 308, conductor 561, contact and engaged with wiper 505, contacts 532 and the winding of magnet 515 to battery, and at contacts 309 a point in the circuit of all-links-busy relay 500 is opened. In energizing, magnet 515 opens a point in the normal operating circuit of the distributor start relay I0 at contacts 516.

In operating completely (second step), at contacts I6I and I63, relay I60 opens its previously traced first-step operating circuit, contacts I64 removes ground from the distributor start conductor I90 and relay 5I0restores. In restoring contacts 5I I, relay 5I0 closes a point in the normal operating circuit of magnet 515, at contacts 5I3 the circuit to relay 520 is opened allowing it to restore, at contacts 5I4, a ground is removed from the multiple circuit of relay 500, at contacts 5I5 ground is removed from the previously opened circuit of relay 550 and at contacts 5I6 the preenergizing and hold circuit of relay 550 is opened, allowing relay 550 to restore. In restoring, relay 550 opens the energizing circuit of relay 300 at contacts 55I and at contacts 553 opens the circuit to meter 585. Relay 300, however, remains energized over its previously traced locking circuit.

In restoring, relay 420 opens the circuit to relay 530 at contacts 52I. In restoring, relay 530 opens the circuit to relay 320 at contacts 53I, at contacts 532 opens the holding circuit for magnet 515, allowing magnet 515 to restore and rotate its pulse.

wipers one step. At contacts 535 a ground is removed from the multiple circuit to relay 560 and at contacts 536 the operating circuit of magnet 390 is further opened. Magnet 515 will rotate its wipers until wiper 505 encounters a contact (each corresponding to a finder-connector link) which contains no ground potential and stops thereon.

In restoring, relay 320 opens contacts 32I to remove the bridge from relay 330, but relay 330 remains operated from the closed loop of subscriber D. At contacts 322 the energizing circuit of relay 300 is further opened by relay 320, but relay 300 remains operated over a previously traced circuit from ground at contacts 34I. At contacts 323 relay 320 further opens the operate circuit of relay 550 and at contacts 324 the energizing circuit of motor magnet 390 is further opened.

As previously mentioned, dial tone has been transmitted back to the calling subscriber which is an indication that the desired number may be dialed and in this case the two-digit number 32 that has been assigned subscriber B will be dialed.

The tens digit 3 is dialed and the line relay 330 (energized at the beginning of dialing) will deenergize and energize upon receipt of each pulse, for a total of three times each. At the beginning of the first pulse and upon deene'rgi'zing, relay 330 opens the circuit to relay 340 at contacts 33I, but relay 340 is slow-'to release and therefore holds operated during dialing. At contacts 332 a circuit is completed to relay 410 and motor magnet 490, these circuits extending respectively from ground at contacts 332, contacts 342, conductor 366, contacts 481, 435, to the left over conductor 368, contacts 352, conductor 361 and the Winding of relay 410 to battery and from ground at contacts 332, contacts 342, conductor 366, contacts 481, 435, to the right over conductor 358 and through the winding of magnet 490 to battery.

In operating, relay 410 completes an obvious circuit to relay 460 at contacts 4', at contacts 412 ground is removed from wipers 468 and 469 during the pulsing period and at contacts 413, relay 410 completes a circuit for itself effective during pulsing independent of the busy relay contacts 435. Motor magnet 490 energizes and at contacts 46I opens a point in its interrupter circuit. The interrupter springs of the dialing mechanism have closed and the circuit is again completed to line relay 330 which reenergizes thus releasing magnet 490 and ending the first In operating contacts 462, relay 480 prepares a circuit to the busy relay 430 and at contacts 464 the pulsing circuit is maintained complete.

At the end of the first pulse and in operating, relay 330 closes the circuit to relay 340 at contacts 33I and at contacts 332 opens the pulsing circuit to motor magnet 490 and relay 410. Relay 410 remains operated, however, due to its slow-to-release characteristics.

As previously stated, wipers 465 to 469, inclusive, are resting on the home" or 26th position of the rotary switch actuated by motor magnet 490, therefore, as magnet 490 restores, wipers 465 to 409 inclusive are advanced one step, with the lower halves of the wipers disengaging their respective contacts and the upper halves of the wipers engaging the first contact of each bank. Dir-normal springs 415 close as the wipers leave their home positions and complete a circuit to relay 350.

In operating contacts 35!, relay 350 removes dial tone from the calling line, at contacts 352 the former energizing circuit for relay 410 is opened, at contacts 353 a ground is maintained on the conductor from the seized finder to a contact of wiper 505, at contacts 354 ground is removed from the conductor to the all-linksbusy relay 506 and at contacts 355 a point in the self-interrupter circuit to magnet 40!! is prepared.

At the beginning of the second pulse, the circuit to line relay 330 is again opened, which upon deenergizing completes the formerly traced energizing circuit to motor magnet 490 and the holding circuit to relay 410 at contacts 332. However, the circuit path to the latter has been altered with the respect that closed 413 have replaced opened contacts 352. This has no apparent effect because as previously stated, relay 416 remains operated during pulsing of each digit dialed. Magnet 406 energizes and opens its self-interrupter circuit at contacts 40!. This interrupter circuit has no effect on the operation at the present and will be discussed later. At the end of the second pulse line relay 330 again energizes and opens the circuit to magnet 466 at contacts 332. In restoring, magnet 493 rotates wipers 465 to 466 inclusive, a second step, at which time the wipers are resting on the second contact of the wipers respective banks.

At the beginning of the third pulse, line relay 636 again deenergizes and completes a circuit, by way of contacts 332, to motor magnet 460 which then energizes. At the end of the third pulse relay 330 again energizes and opens the circuit to magnet 460 at contacts 332. In restoring, magnet 490 rotates wipers 465 to 460 inclusive, a third step, at which time the wipers are resting on the third contact of the wipers respective banks. The dialing of the tens digit 3 has now been completed and the circuit to relay 416 has been opened at contacts 332, thus relay 416 will restore before the second digit has been dialed.

restoring, relay 410 opens the circuit to relay 460 at contacts 41!, thereby allowing relay 466 to restore, at contacts 412 ground is restored to wipers 466 and 466 and a circuit is thereby completed to relay 400, this circuit extending from ground at contacts 306, conductor 365, contacts 412, wiper 468 and engaged contact. conductor 346, contact 384 and through the winding of relay 400 to battery. In restoring contacts 46!, relay 460 prepares a circuit for the lower winding of relay 480, at contacts 462 the circuit to the busy relay 430 is opened.

In operating contacts 402 and 404, relay 400 has prepared for ringing current to be transmitted over the positive talking conductor, which eventually will serve to cause the ringer of station E to operate. As the ringer for station E is on the opposite side of the line, this ringer will not operate. At contacts 405, relay 400 completes its own obvious locking circuit and at contacts 406 a circuit is completed to motor magnet 490, this circuit extending from ground at contacts 306, conductor 365, contacts 412, Wiper 469 and its engaged contact, contacts 406, conductor 318, contacts 381, conductor 316, contacts 488, 49! and the winding of magnet 490 to battery.

In operating, magnet 490 opens its own energizing circuit at contact 49! and thereby restores.

In restoring, magnet 490 rotates wipers 465, to

466 inclusive, one step and closes contacts 49! but the circuit to magnet 490 is now open a wiper 469 is resting on an unused (fourth) contact. However, as wiper 466 engages its next (fourth) contact a circuit is completed to relay 380, this circuit extending from ground at contacts 306, conductor 365, contacts 412, wiper 4 68 and its engaged contact, conductor 349 and through the winding of relay 380 to battery.

In operating contacts 38! relay 36 prepares a circuit for the cut-through relay 486, at contacts 332 a circuit is prepared for the lower winding of the switch-through relay 480, at contacts 363 a circuit is prepared for Executive cut-in which will be discussed later, at contacts 384 the operate circuit of relay 400 is opened, at contacts 305 a locking circuit is completed for relay 380, at contacts 366 a circuit is prepared for relay 410 and at contacts 331 the line-group interrupter circuit to magnet 406 is opened.

Before continuing with the present description, it is thought that the busy test circuit should be described more in detail. When calling into the first line group, as either the first digits 3 or 4 of the call number are dialed, relay 360 is operated and at contacts 38! completes a busy test circuit to the busy relay 430 from the 4th contact engaged with wiper 461, conductor 338, contacts 33!, conductor 330 contacts 462 and through the winding of busy relay 430 to battery. Now, when calling into the second line group, as either the second digits 5 or 6 of the call number are dialed, relay 366 is not operated (because contacts 5 and 6 correspond to lines of the first group which may be busy at the time) until magnet 400 has automatically stepped all its associated wipers to their 15th contacts, at which time relay 380 is operated and at contact 38! completes the above traced busy test circuit. It will be noted that when the first digit of the call number to either line group is 3 or 5, relay 406 will operate to reverse the ring. When the first digit 3 is dialed and after relay 400 operates, magnet 490 steps its wipers to the 4th contacts to operate relay 330. When the first digit 5 is dialed and after relay 460 operates, magnet 436 steps its wipers to the 6th and subsequently to the 15th contacts before relay 38 operates.

The system is now ready for the second or units digit 2, of the call number 32, to be dialed. As the digit 2 is dialed, line relay 330 (energized at the beginning of dialing) will deenergize and energize upon receipt of each pulse, for a total of two times each. At the beginning of the first pulse and upon deenergizing, relay 330 opens the circuit to relay 34 at contacts 33!, but as relay 34 is slow-to-release, it will hold operated during dialing. At contacts 332 a circuit is completed to relay 410 and motor magnet 490, these circuits extend respectively; from ground at contacts 332, contacts 342, conductor 366, contacts 461, 435, to the left over conductor 368, contacts 386, conductor 36'! and through the winding of relay 416 to battery; from ground at contacts 332, contacts 342, conductor 366, contacts 481, 435, to the right over conductor 368 and through the winding of magnet 490 to battery.

In operating contacts 41!, relay 410 completes a circuit to relay 460, at contacts 412 ground potential is removed from wipers 4 68 and 469 relays 386 and 466 are locked operated to grounded conductor 365; and at contacts 413 relay 410 slightly alters its previous operate circuit. In operating, magnet 46 opens a point in its interrupter circuit. At the end of the first pulse and in operating, relay 336 opens the circuits to re- .lay 41 and magnet 460. Relay 410, however, is

1! sl'siw-toeleas and do s n t estore duringp lsure 1 o eratin ontacts 52. rela 6 prepar s 8 c cu i rbusy elay .9 and at Contacts 484' the pulsing circuit is maintained complete in ase bu relay 0 h ld o r bef pulsing is completed.

At the beginning of the second pulse and in relee ms. relay 33 i co le t ci cu t to; astt 4911-, a t. 9 n rat ng ope s ts interrupter circuit at contacts 491 which again have no effect, at the present. At the end of the second and. fineu se. lay 3'30 en r s and opens the circuit to magnet 491i and relay 410 at contacts 332,. restoring, magnet 498 rotates w pers, 5 to 4 inclus e, ano e t It i be remembered that at the beginning of the last digit to be dialed, wipers 46.5 through469 were resting on the fourth contact of each respective w ser-bank an hat. he second disit 2 aused the wipers to, rotate two additional steps, so, now it is evident that the wipers are resting on the sixth contactof each respective bank.

In. restoring, relay 410 opens the circuit to. the slave relay 430 at contacts 4'11, at contacts 4'12 ground is restored to wipers 468 and 488 with no effect and at contact 4'13 the holding circuit of re ay 101s opened- D g t tim at wiper 4,61 first enga s it s xt conta a d before the relay 4601 has restored, a busy-test of the called n s made. I he cal ed. ine Should be busy. a ground would be impressed on the called lines control conductor by contacts such as 484. of its associated seized connector. This ground would be encountered by wiper 451 at it sixth contact and complete a circuit to the busy relay 430, this circuit extending from wiper 451 conductor 338, contacts 381, conductor 339, contacts 462 and the winding of'rel ay 430 to battery. Relay 480, in operating, would close contact 431 for transmitting busy tone out over the positive talking conductor to the calling subscriber, a more detailed description of connection to a busy line being described: hereinafter. However, for the present operation, it will be assumed that the called line is not busy, therefore no ground will be encountered by wiper 451, and busy relay 430 will not operate.

Inrestoring, atcontacts 461 relay 460 completes an operative series circuit to the cutthroughrelay 480 by way of its lower winding andthe line and cut-off relay- 140 this circuit extending from ground at contacts 382, conductor 311, down to contacts 455, contacts 432, through 'the lowerwinding of relay 480, contacts 486, 461-, conductor 339, contacts 381, conductor 338, wiper 481: and its associated contact term-inating conductor 188, cable (2-180, conductor 186, contacts 1 1:8- and the lower winding of relay 140. tobattery, Inoperating, relay 140- opens thecircuit to its upper winding at contacts 141, at contacts 142 ground is removed from the positivetalk-ing conductor, at contacts 143- subscriber B is busied at the finder banks, and at contacts 144, ground is removed from the distributor start conductor toprevent the distributor from starting a finder.

In operating, relay-480 first closestv contacts 485 and completes an operative locking circuit forrelay 480 by way of its upper winding, this circuit extending from ground at contacts 382, conductor-3'11, 3: contacts 485 and through the winding ofrelay-480- to battery. At contacts481, relay 480 prepares a circuit for ring-back tone, at contacts 482- and 483 the talking conductors of the called subscriber are connected with those of the seized connector and a circuit is conipleted for ringing current, this circuit extending from the grounded ringer of subscriber B, the positive talking conductor, contacts 112, 118, conductor 184, cable 0-180, conductor 184, sixth bank contact engaged with wiper 466, contacts 483', 424, 402 and down through the lower winding of the ring cut-ofi relay 420 to interrupted generator. At contacts 484, relay 480 applies a ground to prepare a circuit through the upper winding of relay 420' and also provides an additional busying ground on the control conductor of subscriber B. At contacts 486, relay 480 opens the energizing circuit through its lower winding, at contact 481 the pulsing circuit is opened and at contacts 488- the interrupter circuit to motor magnet 490 is opened.

After a normal interval of ringing over the previously traced circuit at station B, subscriber B answers the call by removing his receiver. The removal ofthe receiver at station E closes theswitch-hook springs (not shown) at the station and completes a direct current circuit through the lower winding of ring cut-oft relay 420- foroperating the relay. This circuit extends from ground at contacts 404, 421, 482, wiper 465 and its engaged sixth contact, conductor I81, cable 0-180, conductor 181, contacts 113, 111, negative talking conductor, switch-hook springs at station E, positive talking conductor contacts 1'12, 116, conductor 184-, cable C-', conductor 184, wiper 468. and its engaged sixth contact, contacts 483, 42-4, 402 and through the lower windingof relay 420 to battery at interrupter generator.

Inoperating, relay' 420 locks itself operated by closing its 32" contacts 426, this circuit extendihg from ground at contacts 484, conductor 338, contacts 381, conductor 3-39, :11 contacts 428 and through the upper winding of relay 420 to battery. At contacts 423-, and 424, ring-back tone and ringing current areremoved from the calling and called: line respectively, at contacts 422 and 425 the back bridge relay 4:10 is connected acrossthecalled line and the talking conductors of the calling and called line are connected so that. conversation may proceed. Line relay: 330: supplies talking battery for the calling partyand back bridge relay 410: supplies. talking battery for the called party.

After completion of conversation, both stations B: and D replace their receivers, The replacing of the receiver at station D disconnects the equipment inthe. following; manner:

The circuit. is. opened; to. line relay 330- which restores and. opens the circuit to the hold' relay 340 to contacts 331.. Relay 340, in restoring, releases contacts 341 and opens the locking circuit torelay-300; and at contacts 343- prepares the-self interrupted homing circuit of motor magnet 490-. The removal of ground, at contacts 341 also releases line and cut-off relay 1801 In restoring, relay- 300: opens the locking circuits of. relays 38,0 and1400 at contacts 308- and at contacts 3118 removesone of; the ground connections from guard lead 581:. Relay 38,0, in-restoring removes ground from conductors 31.1. and. 339 by. way of contacts 381 and 382, thereby opening the circuits to relays. 420- and; 480 In: restoring contacts 484, relay 490 opens the circuit to relay 140, which restores and at contacts 488 completes the homing circuit to magnet 490, this circuit extending from ground at off-normal springs 4'15, conductor 315; contacts 355; 343, conductor 3J6, contacts 488', 491' and through the winding of mag,-

net 496 to battery. Magnet 496 energizes and opens its circuit repeatedly until it has stepped wipers 465 to 469 inclusive to the 26th of home position, at which time off-normal springs 415 open and, the circuits to magnet 496 and relay 356 are maintained open. Relay 426 has restored and the equipment is again at rest and ready for future calls.

Executive cut-in Station A is shown as being assigned to an executive and is equipped with a non-locking key such as I18, which provides the executive with executive cut-in on busy lines. This special feature will function as described in the following paragraphs.

It will be assumed that the subscriber at station B has received or initiated a call and is in a busy condition. A finder-connector identical to the one shown in Figures 3 and 4 will be in use and associated with station B.

Assuming further that this particular executive desires to call station B, his call will be initiated and handled in the same manneras described in the section entitled Regular P. A. X service, but stopping at the point in the operation where the last digit 2 of the call number 32 has been dialed and before the release of the slave relay such as 466. It will also be assumed that the illustrated finder-connector link in Figures 3 and 4, will be used in handling the call placed by said executive.

Continuing now with the explanation: After the last pulse of the dialed digit 2 has been re ceived and motor magnet 496 has advanced wipers 465 to 469 inclusive, the wipers are engaged with their respective sixth contacts. The circuit to relay 416 has been opened at contacts 332 by the line relay 336 and relay 416 restores.

In restoring, relay 416 opens the circuit to slave relay 466, but relay 466 is slow-to-release and does not restore immediately, thereby utilizing this time interval to test for busy. As previously stated, station B is busy and therefore wipers 461 will encounter ground at its sixth contact which then completes a circuit for the busy relay 436, this circuit extending from the grounded control conductor, wiper 461 and engaged contact, conductor 338, contacts 38I, conductor 333, contacts 432 and the winding of relay 436 to battery..

In operating contacts 43I, relay 436 completes a previously traced busy tone circuit to station A, at contacts 432 an energizing circuit is opened to the lower winding of relay 486 and at contacts 433, relay 436 prepares a locking circuit for itself. In restoring as the armature of contact 462 starts to release, a locking circuit is completed for relay 436 by relay 460, this circuit extending from ground at contacts 332, conductor 311, contact 455, 433, 456, 463 and through the winding of relay 436 to battery.

After hearing busy tone, the executive momentarily depresses his non-locking key I18, thus completing a circuit to the cut-in relay 456, this circuit extending from ground at key I18, conductor I69, cable C-I16, conductor I89, the fifth contact of the rotary finder switch and wiper 323, contacts 363, 36I, conductor 331, contacts 443 and the winding of relay 456 to battery.

In operating, relay 456 completes the extension of station A with station B at contacts 45I and 453, at contacts 452, busy tone is removed from the calling line, at contacts 454 and 455, the holding circuit of relay 436 is changed back to the original busy ground on the contact of the called line and at contacts 456 a circuit is completed for relay 446 in series with relay 436. The circuit for these two relays may be traced as follows: From ground on wiper 461, conductor 338, contacts 38I, conductor 339, contacts 454, 433, the winding of relay 446, contacts 463 and the winding of relay 436 to battery. In operating, relay 446 supplies a holding ground for the relay 456 by way of contacts 442.

The executive has been connected with station B and condensers C-4 and C-5 may serve as monitoring or talking condensers. The executive may continue to converse with station B or he may request that both parties hang up their receivers, at which time, the busy relay 436 and relay 446 will restore and the cut-through relay 436 will operate and station B is rung and connected directly with the executive, when B answers the ring, in the usual manner. With a small exchange and a limited number of finder-connector links available, the first method is not desirable, because two links would be in use for the duration of the conversation. For that reason, the second method is preferred, because only one link is used and the other is released to handle other calls. Therefore when station B and his called party release their finder-connector link, station E no longer is busy and ground is removed from wiper 461 and relays 436, 446 and 456 restore and at the same time complete a circuit through the lower winding of relay 466 over a path previously traced in the section entitled Regular P. A. X service. The remaining operation of the equipment and the release of the equipment the same as described in the abovementioned section.

It will be noted that this special type of service entitles the executive to cut-in over all regular calls.

At the top of Figure 4 are shown two conductors 331 and 4I5 labeled thuslyTo voice paging. The voice paging equipment is not shown, however, due to certain requirements of the exchange, voice paging may be desired for some stations. A key (such as I18 shown at station A) may be used to start the voice paging equipment in the following manner: when the key such as I18 is depressed, operations of the equipment shown in Figures 1, 3 and 4 will take place as described in the above section up to and including the operation of relay 446, at which time the closing of contacts 44I completes a circuit to the start relay (not shown) of the voice paging equipment. This circuit may be traced as follows: from ground at key I18, conductor I86, cable C-IHl, conductor I83, the 5th contact engaged with wiper 329, contacts 383, 36I, conductor 331, contacts 44!, conductor M5 and through the winding of the voice paging start relay (not shown) to battery. The start relay then locks operated to conductor 331, by passing contacts 44 I.

Upon completion of the voice paging, the operated equipment in Figures 1, 3 and 4 restore as described in the above section.

Code call The ensuing description of the equipment will cover the addition of the special service feature Code call to the system. This feature is illustrated in Figures 6, 7 and 8 and will be used in combination with Figures 1, 3, 4 and 5, including occasional references to the previous section entitled Regular P. A. X service.

It will be remembered. that certain subscribers whom: it is desired to page by code ringing oi the codecall equipment, are assigned. individual. designated. two-digit code" call numbers and that any subscriber wishing to initiate a code callmust prefix the single digit 1 to the code call number of the desired subscriber; Only certain stations having their extra control: (E CL) con-- ductor markedg by having itconnecte'dto the code call finder, can initiate a code call,- whereas a code call may be answered fromv any station of the system. The prefix digit1 should be dialed then a: slight pause to" wait for a second dial tone before dialing: the code caliznumber, Also, it is to be remembered that the" code calt may be answered dialing thesingledigit2 It: wi'l'i be" assumed that the subscriber at sta-' tiorr A? is an executive and has been assigned the: code call number 33. Assuming also that the subscriber at station C wishes to talk Withthe" executiveand has dialed the executives regular call number 41-, but has been informed by secretary that he" is! somewhere at largeabout the building. The subscriber at station C- can now initiate-a call for the executive by momentarily replacing his: receiver, then remo'ving it and dialing the digit 1- and waiting for dial tone-,. prior tic-dialing the: code callnumber 33.),

Theoperation oftheequipment up to and including? the dialingof the digit 1 is the same as that: inthe: sectionentitled Regular P. A. X service." Ashort review upon completion of dialing, the digit 1-f will reveal that wipers; 465 through 469.- have been advanced to: engage-theirrespective' first contacts; relay 41 0 has restored contacts 412 and completed circuits to relays 38B- and 360= and also opened the circuit to: relay 460;. the circuitfor relay 360- extendsfrom ground at contacts 306, conductor 365, contacts 412 wiper 469 and engagedfirst contact conductor 369- andlthe winding. of relay: 360 to battery; re lay 460. in restoring contacts 461 completes a circuit for the lower. winding'ofrel'ay'480 to opcratein series with parallel connected rel'ays' 63 and. 640 of Figure. 6} this circuit: extendingfrom ground at. contacts 382', conductor 311, contacts 455}. 432,. lower winding. of relay. 460 contacts 486,461, conductor 3'39-, contacts 3'81", conductor 338,, wiper 461' and engaged first contact, conductor IBI, cable C'69'fl, conductor- 181, contacts 131, I521; conductor. 608;. contacts 651 and the windings ofI relays 630" and 640 to battery. In operating contacts 361, ex'ecutivecut-in privileges are removed by relay.- 36D, and at contacts 362 prepares anop'erating circuit for relay 31-6 andthe code call finder. In operating, relay 480' completes its own locking circuit by way of its upper winding. and in contacts 485 over. an obvious path, at contacts 484 a maintaining ground is appliedlfor the relays'63ll' and 6401. and at contacts 481 opens the pulsing circuit to motor magnet 490.

In operating; relay 640 operates at the same time or ahead of 'relay' 630', thereby preventing relay 650 from operatingat the present" time by opening contacts 64!; At-contacts 63!, relay 630 completes a circuit for relay 610, this circuit extending from ground at contacts 63?, contacts 62-1, (its and thewindingofrelays'ifl-to-battem Contacts'63l also clo'se a'preenergizihg circuit for the upper winding of relay GEO-through resistor Rl-3 which renders relay 62'0" extremely fastto operate; At c0ntacts= 632 a matter-y potential is 16 to prepare for stopping the code call finder on the calling line, and at contacts 633 a circuit is prepared for the relay 650.

In operating, relay 6H1 completes an obvious circuit for the motor magnet 665 at contacts S-I F. Magnet 66 5*, in operating, opens the circuitto relay 6I0 by way of contacts 666'. In restoring, relay 6H] opens the circuit to magnet 665 at contacts 6. In restoring, magnet 665 'completes the circuit to" relay 6H) by way of I 666. In restoring contacts BI'I, relay 61'!) opens the circuit to magnet 665" and in restoring, magnet E565 again completes the circuit to relay SID at contacts 666' and agaih-ro'tateswipers' 6I3 through 616 one more step. This interaction continues until the last release of magnet 665 rotates wiper GIG to engage the contact terminating conductor 364, at which time a circuit is completed for the preene'rg'i'zed' relay 620 in series with relay 310, this circuit extending from ground atrelay 310 and through its winding, conductor 346, contacts 4'34, conductor 345, contacts 362, 383, Wiper 329 and engagedcontact, conductor 364, cable 0-31 I, conductor 364, the contact engaged by wiper GIG, lower winding or relay 620 and contacts 632 to battery;- Relay 626 operates before relay Bill has had time to reoperate' and opens the circuit to relay 6H] at contacts 62!, at contacts 522' the resistance R-3 is shunted to complete an obvious lockingcircuitfor' relay 620 by way of its upper winding and at contacts 623 a ground is applied to the control conductors of station C to maintain the" line andcut-oh relay I operated andtobusy station C to allflincoming calls.

In operating c'ont'a'cts 31F, relay 3i!) initiates the release of" the illustrated finder-connector line'(which has been seized by station C) by releasing relay 300', which now' disconnects the talking' conductors oi station C from the line relay 390' of the regular finder-link at contacts 361 and 36-3- and at contacts 366 ground is removed fromconductor 3 allowing relay 380 torestore. Line relay 3'32)" restores and opens the circuit to slow'fto-rele'a'se relay 340. Relay 33D opens the locking circuit of relay 480 at contacts 382 and -at contacts" 363 opens the circuitto the lower winding of relay 626 which now remains operated over its upper winding, the same contacts ("388 7 Open the; circuit to' relay 31-0. I-n restorin'g contacts 484', relay 480 removes the holding ground from relays 630 and 6401and at contacts 488 the sen-interrupting: circuit for motor magnet 49!) is prepared. Relay 34 II: now has restored and at contacts 383' completes the self-interrupting circuitfor' motor magnet 491T. Magnet 4961cstores" wipers: %65 through 469 to their home" pdsition'in the manner as described inthe section entitled Regular P; A. X service, and offncr-maisprings 41-5-ar'e openedg. thereby breaking the circuit to relay 353. The finder-connector link' is now completely restored and conditioned to: handle: future calls-t Referring now to the code' call equipment, relay 6491' restores ahead of the slow-to-release relay 630-, thereby completing an obvious circuit to relay 650by'way of contacts 64I'. In operating, at" contacts; 651',- relay 650 further opens the circuit to relays 630 and 640', at contacts 65?; ground: is applied to the control conductor 18 I for busying. the code call equipment,. at conapplied for marking the extracontrol condiictor 7 w st 33-point in an-alarm' c u t s p 

